/**
 * Simplex noise generator object. Can generate 1D, 2D, 3D and 4D noise.
 *
 * Ported from Stefan Gustavson's java implementation (http://staffwww.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf) Stefan's excellent paper for details on how this code works.
 *
 * @class SimplexNoise
 * @constructor
 * @param {any} r Optional, random number generator object, it is assumed to have a random() method.
 */
function SimplexNoise(r)
{
	if (r === undefined) {r = Math;}

	this.grad3 = [[1, 1, 0], [-1, 1, 0], [1, -1, 0], [-1, -1, 0],
		[1, 0, 1], [-1, 0, 1], [1, 0, -1], [-1, 0, -1],
		[0, 1, 1], [0, -1, 1], [0, 1, -1], [0, -1, -1]];

	this.grad4 = [[0, 1, 1, 1], [0, 1, 1, -1], [0, 1, -1, 1], [0, 1, -1, -1],
	     [0, -1, 1, 1], [0, -1, 1, -1], [0, -1, -1, 1], [0, -1, -1, -1],
	     [1, 0, 1, 1], [1, 0, 1, -1], [1, 0, -1, 1], [1, 0, -1, -1],
	     [-1, 0, 1, 1], [-1, 0, 1, -1], [-1, 0, -1, 1], [-1, 0, -1, -1],
	     [1, 1, 0, 1], [1, 1, 0, -1], [1, -1, 0, 1], [1, -1, 0, -1],
	     [-1, 1, 0, 1], [-1, 1, 0, -1], [-1, -1, 0, 1], [-1, -1, 0, -1],
	     [1, 1, 1, 0], [1, 1, -1, 0], [1, -1, 1, 0], [1, -1, -1, 0],
	     [-1, 1, 1, 0], [-1, 1, -1, 0], [-1, -1, 1, 0], [-1, -1, -1, 0]];

	this.p = [];
	for (var i = 0; i < 256; i ++)
	{
		this.p[i] = Math.floor(r.random() * 256);
	}
	// To remove the need for index wrapping, double the permutation table length
	this.perm = [];
	for (var i = 0; i < 512; i ++)
	{
		this.perm[i] = this.p[i & 255];
	}

	// A lookup table to traverse the simplex around a given point in 4D.
	// Details can be found where this table is used, in the 4D noise method.
	this.simplex = [
		[0, 1, 2, 3], [0, 1, 3, 2], [0, 0, 0, 0], [0, 2, 3, 1], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [1, 2, 3, 0],
		[0, 2, 1, 3], [0, 0, 0, 0], [0, 3, 1, 2], [0, 3, 2, 1], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [1, 3, 2, 0],
		[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
		[1, 2, 0, 3], [0, 0, 0, 0], [1, 3, 0, 2], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [2, 3, 0, 1], [2, 3, 1, 0],
		[1, 0, 2, 3], [1, 0, 3, 2], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [2, 0, 3, 1], [0, 0, 0, 0], [2, 1, 3, 0],
		[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
		[2, 0, 1, 3], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [3, 0, 1, 2], [3, 0, 2, 1], [0, 0, 0, 0], [3, 1, 2, 0],
		[2, 1, 0, 3], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [3, 1, 0, 2], [0, 0, 0, 0], [3, 2, 0, 1], [3, 2, 1, 0]];
};

SimplexNoise.prototype.dot = function(g, x, y)
{
	return g[0] * x + g[1] * y;
};

SimplexNoise.prototype.dot3 = function(g, x, y, z)
{
	return g[0] * x + g[1] * y + g[2] * z;
};

SimplexNoise.prototype.dot4 = function(g, x, y, z, w)
{
	return g[0] * x + g[1] * y + g[2] * z + g[3] * w;
};

SimplexNoise.prototype.noise = function(xin, yin)
{
	var n0, n1, n2; // Noise contributions from the three corners
	// Skew the input space to determine which simplex cell we're in
	var F2 = 0.5 * (Math.sqrt(3.0) - 1.0);
	var s = (xin + yin) * F2; // Hairy factor for 2D
	var i = Math.floor(xin + s);
	var j = Math.floor(yin + s);
	var G2 = (3.0 - Math.sqrt(3.0)) / 6.0;
	var t = (i + j) * G2;
	var X0 = i - t; // Unskew the cell origin back to (x,y) space
	var Y0 = j - t;
	var x0 = xin - X0; // The x,y distances from the cell origin
	var y0 = yin - Y0;
	// For the 2D case, the simplex shape is an equilateral triangle.
	// Determine which simplex we are in.
	var i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
	if (x0 > y0) {i1 = 1; j1 = 0;} // lower triangle, XY order: (0,0)->(1,0)->(1,1)
	else {i1 = 0; j1 = 1;} // upper triangle, YX order: (0,0)->(0,1)->(1,1)
	// A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
	// a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
	// c = (3-sqrt(3))/6
	var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
	var y1 = y0 - j1 + G2;
	var x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
	var y2 = y0 - 1.0 + 2.0 * G2;
	// Work out the hashed gradient indices of the three simplex corners
	var ii = i & 255;
	var jj = j & 255;
	var gi0 = this.perm[ii + this.perm[jj]] % 12;
	var gi1 = this.perm[ii + i1 + this.perm[jj + j1]] % 12;
	var gi2 = this.perm[ii + 1 + this.perm[jj + 1]] % 12;
	// Calculate the contribution from the three corners
	var t0 = 0.5 - x0 * x0 - y0 * y0;
	if (t0 < 0) {n0 = 0.0;}
	else
	{
		t0 *= t0;
		n0 = t0 * t0 * this.dot(this.grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient
	}
	var t1 = 0.5 - x1 * x1 - y1 * y1;
	if (t1 < 0) {n1 = 0.0;}
	else
	{
		t1 *= t1;
		n1 = t1 * t1 * this.dot(this.grad3[gi1], x1, y1);
	}
	var t2 = 0.5 - x2 * x2 - y2 * y2;
	if (t2 < 0) {n2 = 0.0;}
	else
	{
		t2 *= t2;
		n2 = t2 * t2 * this.dot(this.grad3[gi2], x2, y2);
	}
	// Add contributions from each corner to get the final noise value.
	// The result is scaled to return values in the interval [-1,1].
	return 70.0 * (n0 + n1 + n2);
};

// 3D simplex noise
SimplexNoise.prototype.noise3d = function(xin, yin, zin)
{
	var n0, n1, n2, n3; // Noise contributions from the four corners
	// Skew the input space to determine which simplex cell we're in
	var F3 = 1.0 / 3.0;
	var s = (xin + yin + zin) * F3; // Very nice and simple skew factor for 3D
	var i = Math.floor(xin + s);
	var j = Math.floor(yin + s);
	var k = Math.floor(zin + s);
	var G3 = 1.0 / 6.0; // Very nice and simple unskew factor, too
	var t = (i + j + k) * G3;
	var X0 = i - t; // Unskew the cell origin back to (x,y,z) space
	var Y0 = j - t;
	var Z0 = k - t;
	var x0 = xin - X0; // The x,y,z distances from the cell origin
	var y0 = yin - Y0;
	var z0 = zin - Z0;
	// For the 3D case, the simplex shape is a slightly irregular tetrahedron.
	// Determine which simplex we are in.
	var i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
	var i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords
	if (x0 >= y0)
	{
		if (y0 >= z0)
		{ i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // X Y Z order
		else if (x0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 0; k2 = 1; } // X Z Y order
		else { i1 = 0; j1 = 0; k1 = 1; i2 = 1; j2 = 0; k2 = 1; } // Z X Y order
	}
	else
	{ // x0<y0
		if (y0 < z0) { i1 = 0; j1 = 0; k1 = 1; i2 = 0; j2 = 1; k2 = 1; } // Z Y X order
		else if (x0 < z0) { i1 = 0; j1 = 1; k1 = 0; i2 = 0; j2 = 1; k2 = 1; } // Y Z X order
		else { i1 = 0; j1 = 1; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // Y X Z order
	}
	// A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
	// a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
	// a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
	// c = 1/6.
	var x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
	var y1 = y0 - j1 + G3;
	var z1 = z0 - k1 + G3;
	var x2 = x0 - i2 + 2.0 * G3; // Offsets for third corner in (x,y,z) coords
	var y2 = y0 - j2 + 2.0 * G3;
	var z2 = z0 - k2 + 2.0 * G3;
	var x3 = x0 - 1.0 + 3.0 * G3; // Offsets for last corner in (x,y,z) coords
	var y3 = y0 - 1.0 + 3.0 * G3;
	var z3 = z0 - 1.0 + 3.0 * G3;
	// Work out the hashed gradient indices of the four simplex corners
	var ii = i & 255;
	var jj = j & 255;
	var kk = k & 255;
	var gi0 = this.perm[ii + this.perm[jj + this.perm[kk]]] % 12;
	var gi1 = this.perm[ii + i1 + this.perm[jj + j1 + this.perm[kk + k1]]] % 12;
	var gi2 = this.perm[ii + i2 + this.perm[jj + j2 + this.perm[kk + k2]]] % 12;
	var gi3 = this.perm[ii + 1 + this.perm[jj + 1 + this.perm[kk + 1]]] % 12;
	// Calculate the contribution from the four corners
	var t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0;
	if (t0 < 0) {n0 = 0.0;}
	else
	{
		t0 *= t0;
		n0 = t0 * t0 * this.dot3(this.grad3[gi0], x0, y0, z0);
	}
	var t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1;
	if (t1 < 0) {n1 = 0.0;}
	else
	{
		t1 *= t1;
		n1 = t1 * t1 * this.dot3(this.grad3[gi1], x1, y1, z1);
	}
	var t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2;
	if (t2 < 0) {n2 = 0.0;}
	else
	{
		t2 *= t2;
		n2 = t2 * t2 * this.dot3(this.grad3[gi2], x2, y2, z2);
	}
	var t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3;
	if (t3 < 0) {n3 = 0.0;}
	else
	{
		t3 *= t3;
		n3 = t3 * t3 * this.dot3(this.grad3[gi3], x3, y3, z3);
	}
	// Add contributions from each corner to get the final noise value.
	// The result is scaled to stay just inside [-1,1]
	return 32.0 * (n0 + n1 + n2 + n3);
};

// 4D simplex noise
SimplexNoise.prototype.noise4d = function( x, y, z, w )
{
	// For faster and easier lookups
	var grad4 = this.grad4;
	var simplex = this.simplex;
	var perm = this.perm;

	// The skewing and unskewing factors are hairy again for the 4D case
	var F4 = (Math.sqrt(5.0) - 1.0) / 4.0;
	var G4 = (5.0 - Math.sqrt(5.0)) / 20.0;
	var n0, n1, n2, n3, n4; // Noise contributions from the five corners
	// Skew the (x,y,z,w) space to determine which cell of 24 simplices we're in
	var s = (x + y + z + w) * F4; // Factor for 4D skewing
	var i = Math.floor(x + s);
	var j = Math.floor(y + s);
	var k = Math.floor(z + s);
	var l = Math.floor(w + s);
	var t = (i + j + k + l) * G4; // Factor for 4D unskewing
	var X0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
	var Y0 = j - t;
	var Z0 = k - t;
	var W0 = l - t;
	var x0 = x - X0; // The x,y,z,w distances from the cell origin
	var y0 = y - Y0;
	var z0 = z - Z0;
	var w0 = w - W0;

	// For the 4D case, the simplex is a 4D shape I won't even try to describe.
	// To find out which of the 24 possible simplices we're in, we need to
	// determine the magnitude ordering of x0, y0, z0 and w0.
	// The method below is a good way of finding the ordering of x,y,z,w and
	// then find the correct traversal order for the simplex we’re in.
	// First, six pair-wise comparisons are performed between each possible pair
	// of the four coordinates, and the results are used to add up binary bits
	// for an integer index.
	var c1 = x0 > y0 ? 32 : 0;
	var c2 = x0 > z0 ? 16 : 0;
	var c3 = y0 > z0 ? 8 : 0;
	var c4 = x0 > w0 ? 4 : 0;
	var c5 = y0 > w0 ? 2 : 0;
	var c6 = z0 > w0 ? 1 : 0;
	var c = c1 + c2 + c3 + c4 + c5 + c6;
	var i1, j1, k1, l1; // The integer offsets for the second simplex corner
	var i2, j2, k2, l2; // The integer offsets for the third simplex corner
	var i3, j3, k3, l3; // The integer offsets for the fourth simplex corner
	// simplex[c] is a 4-vector with the numbers 0, 1, 2 and 3 in some order.
	// Many values of c will never occur, since e.g. x>y>z>w makes x<z, y<w and x<w
	// impossible. Only the 24 indices which have non-zero entries make any sense.
	// We use a thresholding to set the coordinates in turn from the largest magnitude.
	// The number 3 in the "simplex" array is at the position of the largest coordinate.
	i1 = simplex[c][0] >= 3 ? 1 : 0;
	j1 = simplex[c][1] >= 3 ? 1 : 0;
	k1 = simplex[c][2] >= 3 ? 1 : 0;
	l1 = simplex[c][3] >= 3 ? 1 : 0;
	// The number 2 in the "simplex" array is at the second largest coordinate.
	i2 = simplex[c][0] >= 2 ? 1 : 0;
	j2 = simplex[c][1] >= 2 ? 1 : 0; k2 = simplex[c][2] >= 2 ? 1 : 0;
	l2 = simplex[c][3] >= 2 ? 1 : 0;
	// The number 1 in the "simplex" array is at the second smallest coordinate.
	i3 = simplex[c][0] >= 1 ? 1 : 0;
	j3 = simplex[c][1] >= 1 ? 1 : 0;
	k3 = simplex[c][2] >= 1 ? 1 : 0;
	l3 = simplex[c][3] >= 1 ? 1 : 0;
	// The fifth corner has all coordinate offsets = 1, so no need to look that up.
	var x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
	var y1 = y0 - j1 + G4;
	var z1 = z0 - k1 + G4;
	var w1 = w0 - l1 + G4;
	var x2 = x0 - i2 + 2.0 * G4; // Offsets for third corner in (x,y,z,w) coords
	var y2 = y0 - j2 + 2.0 * G4;
	var z2 = z0 - k2 + 2.0 * G4;
	var w2 = w0 - l2 + 2.0 * G4;
	var x3 = x0 - i3 + 3.0 * G4; // Offsets for fourth corner in (x,y,z,w) coords
	var y3 = y0 - j3 + 3.0 * G4;
	var z3 = z0 - k3 + 3.0 * G4;
	var w3 = w0 - l3 + 3.0 * G4;
	var x4 = x0 - 1.0 + 4.0 * G4; // Offsets for last corner in (x,y,z,w) coords
	var y4 = y0 - 1.0 + 4.0 * G4;
	var z4 = z0 - 1.0 + 4.0 * G4;
	var w4 = w0 - 1.0 + 4.0 * G4;
	// Work out the hashed gradient indices of the five simplex corners
	var ii = i & 255;
	var jj = j & 255;
	var kk = k & 255;
	var ll = l & 255;
	var gi0 = perm[ii + perm[jj + perm[kk + perm[ll]]]] % 32;
	var gi1 = perm[ii + i1 + perm[jj + j1 + perm[kk + k1 + perm[ll + l1]]]] % 32;
	var gi2 = perm[ii + i2 + perm[jj + j2 + perm[kk + k2 + perm[ll + l2]]]] % 32;
	var gi3 = perm[ii + i3 + perm[jj + j3 + perm[kk + k3 + perm[ll + l3]]]] % 32;
	var gi4 = perm[ii + 1 + perm[jj + 1 + perm[kk + 1 + perm[ll + 1]]]] % 32;
	// Calculate the contribution from the five corners
	var t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0 - w0 * w0;
	if (t0 < 0) {n0 = 0.0;}
	else
	{
		t0 *= t0;
		n0 = t0 * t0 * this.dot4(grad4[gi0], x0, y0, z0, w0);
	}
	var t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1 - w1 * w1;
	if (t1 < 0) {n1 = 0.0;}
	else
	{
		t1 *= t1;
		n1 = t1 * t1 * this.dot4(grad4[gi1], x1, y1, z1, w1);
	}
	var t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2 - w2 * w2;
	if (t2 < 0) {n2 = 0.0;}
	else
	{
		t2 *= t2;
		n2 = t2 * t2 * this.dot4(grad4[gi2], x2, y2, z2, w2);
	} var t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3 - w3 * w3;
	if (t3 < 0) {n3 = 0.0;}
	else
	{
		t3 *= t3;
		n3 = t3 * t3 * this.dot4(grad4[gi3], x3, y3, z3, w3);
	}
	var t4 = 0.6 - x4 * x4 - y4 * y4 - z4 * z4 - w4 * w4;
	if (t4 < 0) {n4 = 0.0;}
	else
	{
		t4 *= t4;
		n4 = t4 * t4 * this.dot4(grad4[gi4], x4, y4, z4, w4);
	}
	// Sum up and scale the result to cover the range [-1,1]
	return 27.0 * (n0 + n1 + n2 + n3 + n4);
};

export {SimplexNoise};
